A very common question is, are baking powder and bicarbonate of soda the same thing? Baking powder and bicarbonate of soda are both leavening agents used in baking, and whilst they both do the same role in the baking process, they are chemically different and this difference is important when considering how to use them and whether or not they can be exchanged for each other in a recipe easily.
Firstly, we will look at the specific difference chemically between bicarbonate of soda and baking powder. The major difference is regarding their acidity level. We will start with bicarbonate of soda, as it is the most likely to cause confusion.
Bicarbonate of soda is a base, and works as a leavening agent due to its mixing with an acid (think in the same way as bicarbonate of soda and vinegar being used to create a volcano like reaction.) The process of mixing acid and bicarbonate of soda creates the bi-product of carbon dioxide, which is what causes the rising in the product.
Bicarbonate of soda is often used for items like cookies and cakes, and will mean that the recipe will include some kind of acid like buttermilk, lemon juice, yoghurt or cream of tartar.
Bicarbonate of soda is very strong (around 3-4 times the strength of baking powder) but it does not mean that more means more lift. If you add too much to the mixture then it will leave excess bicarbonate of soda in the finished product and that produces a metallic and soapy aftertaste.
Baking powder is basically bicarbonate of soda combined with cream of tartar (and sometimes cornstarch). Baking powder is often sold as double acting, which means that the first leavening happens when the baking powder gets wet (which is part of the reason that you can’t make up some mixes in advance) and then the second leavening happens when the mix is heated during baking.
It doesn’t mean that you can’t use baking powder with a recipe with acid in it, as it can work with buttermilk or lemon juice too.
It is possible to substitute one for the other, but it does require very special considerations. You can swap baking powder for bicarbonate of soda, but you will need to increase the amount of acid in the recipe to make sure that the leavening process will still happen. On the flip side, you can swap bicarbonate of soda for baking powder but you will need to increase the amount used by around 4 times. This could cause an increase I. The bitterness of the recipe, so it is important to make sure that you consider the impact, so we would suggest trying it out with different quantities of baking powder.